Individual wires, wire harnesses, or cables having two or more wires or strands are customarily grouped and held adjacent to each other at various points along their lengths by use of cable ties or cable lacing tape. For example, it may be desirable to hold together two or more wires, wire harnesses, cables or other objects, or connect such objects to other structures. In these instances, cable lacing tie assemblies may be used to help ensure the safety and durability of the various components.
Cable ties have become very common and typically are formed from a molded piece of plastic that includes an elongated solid strap connected at one end to a buckle. The strap is intended to be looped around a bundle of wires and then fed into the buckle. In an example, corresponding surfaces on the strap and within the buckle commonly have complementary serrated patterns that can achieve a locking position. Thus, a cable tie buckle often includes a molded locking element or pawl within the passageway to cooperate with molded serrations or teeth along the strap. The buckle may include a separately provided metal pawl to engage the serrations on the strap. Alternatively, the strap may have flat surfaces and the buckle may include a separately provided metal barb or knife-like strap piercing element to cut or bite into the strap and prevent rearward withdrawal of the strap. However, such a barb or knife like strap piercing element is usually destructive to the strap when it cuts or bites into the strap, permanently reducing the strength of the strap and increasing the tendency for the strap to tear through.
Once a strap of a cable tie is passed into the buckle, it may be cut to remove any remaining free end. However, in these instances, the cut section of the molded plastic strap that protrudes from the buckle can present an undesirable, fairly sharp obstruction that may result in abrasion problems with respect to adjacent wire bundles, and may be problematic if one is attempting to pull the wire bundle through an aperture, such as a panel opening. This also can be true of the molded buckle itself, which can be relatively large and may have fairly sharp edges. It should be noted that another drawback of molded plastic cable ties is that, due to their relative rigidity, they generally are not capable of closely hugging irregular or rectangular shapes, as may occur when bundling wires, wire harnesses or cables, or connecting them to other structures.
In use, a cable tie can be subjected to elevated temperatures, such as for instance in the aerospace environment, which may reach as high as 400° F. These elevated temperatures can cause a common cable tie, which is typically molded from thermoplastic material, such as nylon, to creep or lose structural integrity. In addition, the integral locking element or pawl that engages the strap then may yield, allowing the wire bundle to separate or come loose. The locking element or pawl generally will be constructed to be deflectable, so as to reduce the strap insertion force, but this also compromises the ability to retain the strap, especially at high temperatures. Cable ties that have a separately provided metal locking element or pawl usually are intended to provide for increased retention, even at elevated temperatures, but these structures typically require higher insertion forces when passing over the metal element.
Because of many of the above drawbacks associated with plastic molded cable ties, in areas where elevated levels of safety are required, such as in the military and commercial aircraft industries, the aerospace industry, as well as in some marine environments, there is a preference to use a procedure known as “cable lacing” for securing or bundling wires, wiring harnesses or cables. Cable lacing includes looping a material commonly referred to as “cable lacing tape” around wires, wire harnesses or cables and tying knots in the cable lacing tape, either in discrete locations along the length of the bundle, referred to as spot ties, or in a running format with the cable lacing tape continuing along the bundle between knot locations.
Modern cable lacing tapes typically are a thin, relatively flat, woven, or braided cord, often referred to as a “tape,” having filaments that may be made of materials such as nylon, polyester or aramid fiber, and which may be impregnated with coatings to enhance particular performance characteristics. Materials such as aramid fiber provide good tensile strength, while being non-flammable, highly resistant to fluids and lubricants, and able to perform in extreme temperature environments, such as from approximately −65° F. to 500° F. However, cable lacing has drawbacks in that the cable lacing tape typically is tied by hand in a costly, labor-intensive, and time-consuming process. Due to these problems, several attempts have been made to automate the cable lacing process.
One such device for automated knot tying is described in U.S. Pat. No. 6,648,378, which generally describes a hand-held housing and a knot-tying mechanism within that housing comprising a plurality of carriage rings, for wrapping the filament around the workpiece. A shuttle moves the filament between the carriage rings and along the workpiece, and a plurality of hooks pull the filament away from the workpiece. The operation is finished by cinching, cutting, and reloading so that the resulting knot is discrete and secure.
Another automated device is disclosed in U.S. Pat. No. 8,622,440, which is directed to a knot tying device for tying a filament in a knot around an article and a filament delivery device from which is drawn the filament. The filament delivery device may be in the form of a cartridge having a housing sized and arranged to be releasably attached to the knot tying device where the housing has an opening through which pre-cut or loosely coupled lengths of the filament can be drawn. The knot tying device includes a shuttle attachable to the filament where the shuttle is caused to be moved during a knot tying process around an article to be tied and a device for at least pulling the filament away from the article at appropriate times during the knot tying process.